Group scheduling in wireless communication systems

ABSTRACT

A wireless communication network ( 100 ) wherein information is communicated in frames comprising multiple sub-frames, including grouping a terminal in first and second groups, assigning the first and second groups to less than all sub-frames in a frame, assigning a control channel of at least one assigned sub-frame to the first and second groups

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications andmore particularly to group scheduling mobile terminals in wirelesscommunication systems and corresponding methods.

BACKGROUND OF THE DISCLOSURE

In wireless communication systems, it is desirable to reduce overheadassociated with signaling for voice and data services, systeminformation, control, etc. In traditional GSM and UMTS systems, bearerestablishment is enabled through dedicated signaling. The bearer definesradio parameters, for example, time slot, frequency, code, etc.,associated with a channel during a call. In voice communications forexample a dedicated channel is assigned to each user. In High SpeedDownlink Packet Access (HSDPA) systems, transport format andmodulation/coding parameters (TFRI) are provided using dedicated controlsignaling on a shared control channel, wherein the shared controlchannel also signals the code channel assigned to the user.

In some data only (DO) systems, voice is served over IP (VoIP). It isknown to improve such systems for VoIP traffic using hybrid automaticrepeat request (HARQ) error correction schemes and smaller packet sizes.While VoIP users have the same benefits of advanced link adaptation andstatistical multiplexing as data users, the greatly increased number ofusers that may be served because of the smaller voice packet sizesplaces a burden on control and feedback mechanisms of the system. It canbe easily envisioned, for example, that 30 times as many voice packetscould be served in a given frame than data packets. There are typicallyabout 1500 bytes for data and about 40-50 bytes for voice. Presentresource allocation and channel quality feedback and acknowledgmentmechanisms however are not designed to handle such a large number ofallocations.

In 802.16e systems, it is known to use a telescoping control channelthat expands to include as many assignments as necessary for resourceallocation. However, such an expansion mechanism does not addressfeedback or the fact that the entire downlink may be consumed forcontrol information. Another mitigating mechanism is to group severalvoice packets together for transmission to a particular user.Unfortunately, this sort of packaging mechanism can adversely affectspeech quality when a transmission is not received, since longer periodsof speech are lost or corrupted. Thus there is a need for increasing thenumber of VoIP users supported while reducing control and feedbackoverhead. In packet based systems the term “data” is meant to signifypayload information for any service, voice or data.

The various aspects, features and advantages of the present disclosurewill become more fully apparent to those having ordinary skill in theart upon careful consideration of the following Detailed Descriptionthereof with the accompanying drawings described below. The drawings mayhave been simplified for clarity and are not necessarily drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative wireless communication network.

FIG. 2 is an illustrative sequence of radio frames each comprising aplurality of sub-frames.

FIG. 3 is an illustrative sub-frame including a control and datachannels portions.

FIG. 4 illustrates a first resource allocation scheme.

FIG. 5 illustrates another resource allocation scheme.

FIG. 6 illustrates yet another resource allocation scheme.

DETAILED DESCRIPTION

FIG. 1 is a wireless digital communication system 100 comprising aplurality of base transceiver stations 110 providing wirelesscommunication service, including voice and/or data service, to wirelessterminals 102 over corresponding regions or cellular areas. The basetransceiver stations, also referred to by other names such as a “Node B”depending on the system type, are communicably coupled to a controller120 and to other entities that are not shown but are well known by thosehaving ordinary skill in the art. In FIG. 1, each base transceiverstation includes a scheduling entity 112 for radio resource schedulingamong the wireless communication terminals within the network. Exemplarycommunication systems include, but are not limited to, developingUniversal Mobile Telecommunications System (UMTS) networks, EvolvedUniversal Terrestrial Radio Access (E-UTRA) networks, and other OFDMbased networks.

E-UTRA and other communication protocols are being developed to supportdelivery of voice services over a packet domain, in contrast to thetraditional support of voice over circuit switched domain. Thus there isinterest in schemes that support voice traffic over a shared radiochannel, wherein multiple users share the time and frequency resourcesof the radio interface. In order to attain a significant increase incapacity with E-UTRA, efficient radio resource allocation schemes willlikely be required to accommodate voice traffic. In these and otherapplications, including data applications, it is generally desirablethat control signaling overhead be minimized while offering flexibilityto the scheduler at the network. In the general sense, it is useful todefine a mechanism to efficiently signal resource allocation and relatedcontrol channel information to multiple terminals applicable to abroadband wireless system, relying on shared channels for delivery ofany service using packet based transmission.

FIG. 2 illustrates a sequence of radio frames 200 useful forcommunicating in wireless digital communication systems. In FIG. 2, theframe sequence generally comprises a plurality of frames 210, 220, 230,wherein each frame comprises a plurality of sub-frames. For example,frame 210 comprises a sub-frame 212 having a resource assignment controlchannel portion within a control channel portion 214 and a data channelportion 216. In some embodiments, the frames constitute a repeatingsequence of frames, wherein the repeating sequence may be a periodic oraperiodic repeating sequence.

FIG. 3 is a more detailed illustration of a sub-frame 300 comprising aresource assignment control portion 310 and a data portion 320. Theresource assignment control portion 310 includes downlink resourceassignment information 312, uplink resource assignment information 314and feedback information 316, among other information. The feedbackinformation may relate to uplink and/or downlink communications, asdiscussed further below.

In one embodiment, a scheduler or other infrastructure entity in awireless communication system groups wireless communication terminals inone or more groups. In one embodiment, the terminals are grouped basedon radio channel conditions associated with the terminals, for example,channel quality information reported by the terminals, Doppler reportedby the terminal, distance from the serving cell, among others. Inanother embodiment, the terminals are grouped based on terminaloperating characteristic other than participation in a commoncommunication session. Exemplary terminal operating characteristicsinclude power headroom of the terminals, or macro diversityconsiderations, terminal capability, service of the terminals, codecrate among other considerations. The groupings of the terminals may alsobe based on combinations of these and other criteria not specificallydisclosed.

Generally, multiple terminals are assigned to corresponding groups. Aterminal may be assigned to more than one group. Terminals may also bere-assigned from one group to a different group, for example, based onchanging conditions used as criteria for the grouping. The terminal mayalso request re-assignment to a different group.

A network entity generally assigns one or more control channels to eachgroup for radio resource assignment. Controls channels used for radioresource assignment are referred to herein as resource or radio resourceassignment control channels, which are distinguished from other types ofcontrol channels. Generally, where there are multiple groups, each grouphas a different control channel or a different combination of controlchannels assigned thereto. Thus in one embodiment, a first controlchannel is assigned to a first group and a second control channel isassigned to a second group.

A network entity sends resource assignment control channel informationto the terminals in the group wherein the control channel informationindicates which frame(s) and corresponding sub-frame(s) that theterminals in the group should monitor for radio resource assignments.The terminals in the group thus monitor the control channel(s)associated with the group to which the terminals are assigned. Theterminals of the group may determine whether a radio resource has beenassigned to the terminal based on information in the resource assignmentcontrol channel, as discussed further below. The resource assigned toeach terminal may be determined based on an implied or explicit mapping,also discussed further below.

In one embodiment, each of the one or more groups is assigned to lessthan all sub-frames constituting a particular frame, wherein a radioresource assignment control channel of at least one assigned sub-frameis assigned to each group. Generally different groups are assigned todifferent sub-frames. In some embodiments, two or more groups may beassigned to the same sub-frame. In embodiments where two or more groupsare assigned to the same sub-frame, the groups are assigned to differentresource assignment control channels within the same sub-frame.

In FIG. 2, for example, a first control channel associated with a firstgroup is assigned to a corresponding sub-frame 212 of frame 210.Generally, the first group could be assigned to multiple sub-frames inthe frame, but not to all sub-frames thereof. Also, generally, eachgroup is assigned to a sub-frame in different frames in the sequence. InFIG. 2, for example, the group may be assigned to sub-frame 212 in frame210 and to sub-frame 232 in frame 230.

Generally, the frames are part of a repeating sequence of frames forpurposes of reading a resource assignment control channel. Each groupmay thus be assigned to less than all sub-frames constituting a frame ina repeating sequence of frames. In some embodiments, the group/sub-frameassignments are periodic, and in other embodiments the assignments arenot periodic. Thus a group may be assigned to the same sub-frame(s) inthe same frame in a sequence of multiple frames. For example, a group isassigned to a first sub-frame in a first frame in each sequence offrames. In another embodiment, a group may be assigned to differentsub-frame(s) in the same frame in the sequence of frames. For example, agroup is assigned to a first sub-frame in a first frame in the firstsequence of frames, and the group is assigned to a second sub-frame inthe first frame in the second sequence of frames. In another embodiment,a group is assigned to same sub-frame(s) in different frames of thesequence of frames. For example, a group is assigned to a firstsub-frame in a first frame in the first sequence of frames, and then thegroup is assigned to the first sub-frame in the second frame in thesecond sequence of frames. More generally, a group may be assigned toevery nth sub-frame in a continuous sequence of frames.

Different types of information may be communicated over the controlchannel. One type of information is radio resource assignmentinformation. Other types include modulation format, coding rate and HARQinformation. Another type of control channel information is feedback,for example, ACK/NACK signaling information. Generally, feedback controlinformation that the terminal sends is on a different control channelthan the control channel indicating radio resource assignment.Information not related to radio resource assignment may be communicatedwith a radio resource indication, for example, in a radio resourceassignment control channel. Alternatively, non-radio resource assignmentinformation may be indicated in a separate portion of a sub-frame, or itmay be known a priori by the terminal.

In FIG. 3, for example, feedback control channel information iscommunicated in bit map 316. Such feedback information, for example,ACK/NACK information, is for previous transmissions by terminals in thegroup or for prior reception by the terminals in the group fortransmissions sent by a network entity. In one embodiment, each terminalin the group is assigned to a location in the bit map, wherein theterminal reads its assigned bit map location in the control channel toobtain the feedback information.

A radio resource may be assigned to at least one terminal of the groupwith radio resource assignment information in the control channel.Generally, the resource assignment information may simultaneously assigndifferent portions of the radio resource to corresponding terminals ofthe group. The resource assignments may be for the uplink or thedownlink. In FIG. 3, downlink assignments are made by the downlinkresource assignment information 312 and uplink assignments are made bythe uplink resource assignment information 314. Also, the radio resourceassignment information may indicate that the radio resource assigned islocated in more than one sub-frame, wherein the assigned sub-frames maybe in the same frame or in different frames on either the uplink ordownlink. For uplink resource assignments, the radio resource assignmentinformation may provide frame/sub-frame offset information.

In EUTRA, radio resources are assigned as a set of sub-carriers over atimeslot. Thus in E-UTRA Scheduling embodiments, for example, the radioresource assignment includes assigning a sub-carrier for a specifiedtime interval. In UMTS scheduling embodiments, the radio resourceassignment includes assigning a channelization code in a frequencychannel for a specified time interval. These radio resource assignmentsare only illustrative and not intended to limit the subject matter ofthe disclosure.

Generally, the radio resource assignment information of the controlchannel identifies at least one terminal to which a radio resource hasbeen assigned. In one embodiment, one or more terminals to which aresource has been assigned are identified by information in the controlchannel. In another embodiment, the identity is a group identityassigned to at least one terminal. In a more particular embodiment, theterminals to which a resource has been assigned are identified and theorder in which the terminals are identified dictates what resource hasbeen assigned. For example, if three of the 5 terminals in a group areidentified as having been assigned a resource, by virtue of theterminals having been referenced by a code or other identifier in thecontrol channel assignment information, the first referenced terminal isassigned a first unique predefined radio resource, the second referencedterminal is assigned a second unique predefined radio resource, and thethird referenced terminal is assigned a third unique predefined radioresource, wherein the unique predefined radio resources are known apriori by the terminals in the group. Thus in this first embodiment,only the identity of the terminals to which an assignment has been madeneeds to be communicated by the scheduler to the group. FIG. 4illustrates a sub-channel 400 comprising a control channel 410 having aresource assignment bit map 420 with locations that are mapped to uniquepredefined radio resources in the data channel 430. Particularly,resource assignment location 422 is associated with radio resource 432and bit map location 424 is associated with radio resource 434. Each ofthe other bit map location is also associated with a corresponding radioresource.

In an alternative embodiment, the control channel assignment informationmay include additional information associated with each terminalreference indicating what resource has been assigned. In thisalternative embodiment, for each assignment, the control channelinformation must identify the terminal and identify the radio resourceassigned. FIG. 5 illustrates a sub-channel 500 comprising a controlchannel 510 having a resource assignment bit map 520 with locations thatare mapped to unique predefined radio resources in the data channel 530.Particularly, resource assignment location 522 includes additional bitdefining radio resource 532 and bit map location 424 includes additionalbit defining radio resource 534. The use of additional bits to definethe radio resources provides the scheduler with greater flexibility inscheduling and allocating radio resources.

In another alternative embodiment, the control channel assignmentinformation includes additional (pointer) information associated witheach terminal indicating where to obtain a resource assignment. FIG. 6illustrates a sub-channel 600 comprising a control channel 610 having aresource assignment bit map 620 with locations that include pointers tounique predefined radio resources in the data channel 630. Particularly,resource assignment location 622 includes additional bits pointing tolocation 626, which defines or identifies radio resource 632. Theresource assignment location 624 includes additional bits pointing tolocation 628, which defines or identifies radio resource 634.

In another embodiment, each terminal in the group is associated with alocation within a bit map that is part of the assignment controlchannel. In FIG. 3, for example, five terminals in a group are eachassociated with a corresponding location in the uplink and downlinkresource assignment control channels. For example, the first terminalreads the first location 318, the second terminal reads the secondlocation 322, etc. in each of the uplink and downlink assignmentchannels. In one embodiment, a unique pre-defined radio resource, knowna priori by each terminal, is associated with each bit map location.According to this exemplary embodiment, the bit map merely needs toindicate whether or not an assignment has been made.

In one embodiment, a communication terminal is grouped in first andsecond groups. For example, one group may be associated with frequencydiverse radio resources and another group associated with frequencyselective radio resources. In one exemplary application, a terminal isassigned to a frequency selective group for a first transmission and toa frequency diverse group for re-transmissions. Alternatively, aterminal may be assigned to a frequency diverse group for firsttransmissions and to a frequency selective group for re-transmissions.In another application, one group may be for receiving compressedinformation and another group for receiving uncompressed information.Multiple grouping may also be based on whether the terminal iscommunicating both data and voice, and more generally whether theterminal is communicating using both longer and shorter data packets.Also terminals may be grouped in more than one group to address overloadconditions. Terminals may also be grouped in multiple groups for otherreasons not explicitly identified herein.

The first and second groups to which the terminal is assigned may beassigned to the same sub-frames or to different sub-frames in the sameor different frames. In embodiments where terminals are grouped in morethan one group, the first and second groups are assigned or associatedwith less than all sub-frames of the same or different frame.

In one embodiment, a terminal is assigned to first and second groupswherein the first and second groups are assigned to the same sub-framesof the same frame. Such a grouping assignment may be suitable forterminals using compressed and uncompressed communications. Thisexemplary grouping assignment is also suitable for terminalssimultaneously using voice and data services. Another application forthis exemplary grouping is to accommodate overload conditions. Anoverload condition may occur when terminals in a particular grouprequire more resources than are available for the group in a particularsub-frame. Thus where resources are unavailable in a sub-frameassociated with the primary group, a terminal may be granted resourcesin a different sub-frame associated with a secondary group. In oneembodiment, a terminal is assigned to first and second groups whereinthe first and second groups are assigned to different sub-frames of thesame frame. Such a grouping assignment may be suitable for terminalssimultaneously using voice and data services. Another application forthis exemplary grouping is to accommodate overload conditions. Inanother embodiment, a terminal is assigned to first and second groupswherein the first and second groups are assigned to the same ordifferent sub-frames of different frames. Such a grouping assignment mayalso be suitable for terminals simultaneously using voice and dataservices.

In one embodiment where a terminal is assigned to first and secondgroups, a control channel is assigned to at least one sub-frame of thefirst and/or second group. In one embodiment, first and second groupsare assigned to common sub-frames of a common frame, and differentcontrol channels are assigned to at least one sub-frame in the first andsecond groups. The control channels may or may not be resourceassignment control channels.

In another embodiment where a terminal is assigned to first and secondgroups, a resource assignment control channel is assigned to at leastone sub-frame of the first and/or second group, and a radio resource isassigned to the terminal grouped in the first and second groups over theresource assignment control channel. The assigned radio resource may bein the same sub-frame as the control channel and/or in one or moredifferent sub-frames of the same or different frame as the sub-frame inwhich the control channel is located. In another embodiment, theassigned radio resource is in at least one of two sub-frame groups,wherein each sub-frame group includes at least one sub-frame and each ofthe first and second groups is associated with a corresponding one ofthe sub-frame groups. The assigned radio resource may be in at least oneof two different sub-frame groups, or the assigned radio resource may bein two or more different sub-frame groups.

In one embodiment, the wireless communication terminal determines aradio resource assignment based on control channel information on anassigned control channel, wherein the control channel informationindicates all possible assignments of first and second radio resourcesto the terminal. Particularly, either one of the first or secondresources may be assigned, or both the first and second resources may beassigned, or neither of the first and second resources may be assigned.

In one embodiment, the radio resource assignment is determined based oncontrol channel information received in first and/or second sub-frames.In one embodiment, for example, an uplink radio resource assignment isdetermined based on control channel information received in the firstsub-frame, and a downlink radio resource assignment is determined basedon control channel information received in the second sub-frame.Non-resource assignment information, for example, modulation format,coding rate, etc., may also be communicated over a control channel anddetermined by the terminal for one or more radio resources assigned tothe terminal. In one embodiment, the non-resource assignment informationmay be located in the data channel portion of a sub-frame, wherein thelocation of the non-resource assignment information is known to theterminal a prior or information is included in the control channelindicating the location of the non-resource assignment information.

In one embodiment, a wireless communication terminal determines whetherit has been assigned first and second radio resources by monitoringfirst and second corresponding control channels. In one particularembodiment, the terminal determines whether it has been assigned thesecond radio resource only if the first radio resource was not assigned.In another particular embodiment, the terminal is assigned a first radioresource through a first control channel and, thereafter, the terminalmonitors a second control channel only if a condition is not satisfiedin connection with the radio resource assigned via the first controlchannel. For example, if the terminal experiences a failed transmissionor reception on the first radio resource, the terminal would monitor thesecond control channel for an alternate radio resource assignment.

In another embodiment, a wireless communication terminal monitors afirst control channel for radio resource assignment information on awireless communication network and, while monitoring the first controlchannel, the terminal obtains information for monitoring a secondcontrol channel on the same wireless communication network. In oneembodiment, the second control channel is different than the firstcontrol channel wherein the terminal may monitor one or both of thefirst and second control channels. In other embodiment, the terminal thesecond control channel instead of the first control channel, wherein thesecond control channel is a modification of the first control channel.An exemplary modification is one such that the modified control channelis capable of assigning resources associated with groups to which theterminal has been associated at an infrastructure entity, for example, abase station scheduler. This additional control channel monitoringinformation may be obtained by reading a broadcast control or otherchannel, or by receiving a dedicated message. Assignment to a secondarygroup may be to accommodate services, for example, voice or data, inaddition to services already used by the terminal. Such a subsequentassignment may also be for addressing overloading conditions. Theterminal may monitor the second channel for radio resource assignmentsor for other information.

In one embodiment, the terminal determines whether the terminal has beenidentified, by at least one of two different identities assigned to theterminal, in the control channel information monitored by the terminal.For example, the terminal may be assigned one or more identities by ascheduler, wherein each identity is associated with a correspondinggroup to which the terminal has been associated by the scheduler. Theterminal may thus use the one or more identities to determine whichradio resources, for example, uplink, downlink, voice, data, firsttransmission, re-transmission, etc., have been assigned.

While the present disclosure and the best modes thereof have beendescribed in a manner establishing possession by the inventors andenabling those of ordinary skill in the art to make and use the same, itwill be understood and appreciated that there are many equivalents tothe exemplary embodiments disclosed herein and that modifications andvariations may be made thereto without departing from the scope andspirit of the inventions, which are to be limited not by the exemplaryembodiments but by the appended claims.

1. A method in a wireless communication infrastructure entity whereininformation is communicated in a frame comprising multiple sub-frames,the method comprising: grouping a first terminal in a first group, andgrouping the first terminal in a second group; assigning the first groupto less than all sub-frames constituting a frame, and assigning thesecond group to less than all sub-frames constituting a frame; assigninga control channel of at least one assigned sub-frame to the first andsecond groups.
 2. The method of claim 1, assigning the first and secondgroups to less than all sub-frames constituting a common frame.
 3. Themethod of claim 2, assigning the first group to different sub-framesthan the second group.
 4. The method of claim 2, assigning the first andsecond groups to common sub-frames of the common frame, assigningdifferent control channels to the first and second groups.
 5. The methodof claim 1, the control channel is a resource assignment controlchannel, assigning a radio resource to the terminal grouped in the firstand second groups.
 6. The method of claim 5, assigning the radioresource in different sub-frames to the terminal.
 7. The method of claim5, assigning the radio resource includes assigning a radio resource inat least one of two sub-frame groups, each sub-frame group including atleast one sub-frame, each of the first and second groups associated witha corresponding one of the sub-frame groups.
 8. The method of claim 7,assigning the radio resource includes assigning the radio resource in atleast one of two different sub-frame groups.
 9. The method of claim 8,assigning the radio resource includes assigning the radio resource in atleast two different sub-frame groups.
 10. A method in a wirelesscommunication terminal wherein information is communicated in a framecomprising multiple sub-frames, the method comprising: determining aradio resource assignment based on control channel information on anassigned control channel, the control channel information indicating allpossible assignments of first and second radio resources to theterminal.
 11. The method of claim 10, determining the radio resourceassignment based on control channel information received in first andsecond different sub-frames.
 12. The method of claim 11, determininguplink radio resource assignment based on control channel informationreceived in the first sub-frame, and determining downlink radio resourceassignment based on control channel information received in the secondsub-frame.
 13. The method of claim 10, determining radio resourceformatting information for first and second radio resources assigned tothe terminal.
 14. The method of claim 10, determining whether theterminal has been assigned first and second radio resources bymonitoring first and second corresponding control channels.
 15. Themethod of claim 14, determining whether the terminal has been assignedthe second radio resource only if the first radio resource was notassigned.
 16. The method of claim 14, determining whether the terminalhas been assigned the second radio resource only if a condition was notsatisfied in association with an assignment of the first radio resource.17. The method of claim 10, determining a radio resource assignmentincludes determining whether the terminal has been identified, by atleast one of two different identities assigned to the terminal, in thecontrol channel information.
 18. A method in a wireless communicationterminal wherein information is communicated in a frame comprisingmultiple sub-frames, the method comprising: monitoring a first controlchannel for radio resource assignment information on a wirelesscommunication network; obtaining monitoring information for a secondcontrol channel on the same wireless communication network whilemonitoring the first control channel.
 19. The method of claim 18,obtaining the monitoring information including obtaining radio resourceassignment control channel information.